Is Water a Barrier to a Low-Carbon Energy Future?

Ask an expert on clean tech what the largest barriers to a low carbon energy future are, and chances are they will list higher technology costs, policy barriers, or the need for new infrastructure to accommodate novel energy sources.

Not convinced? Here’s a few factoids to wet your appetite (pun intended):

The US power sector withdrew as much water from America’s rivers, lakes, and oceans for cooling needs as the country uses to irrigate all agricultural lands, according to MIT Professor Ahmed Ghoniem.

Worldwide, baseload power plants use the same amount of water for cooling as 545 megacities the size of New York City, according to Peter Evans, Director of Global Planning and Strategy for GE. By 2025 as global power demand grows, water needs will rise to 660 New York City’s worth.

Big numbers indeed, and a potentially substantial challenge to a low-carbon energy transition, particularly for new “baseload” or reliable sources of emissions-free power.

Excepting wind and solar photovoltaics, both intermittent energy sources, all other low-carbon power sources need water — LOTS of it — either for cooling needs (as in the case of geothermal, nuclear, solar thermal, or fossil plants with carbon capture) or as their motive force (in the case of hydroelectric and tidal power).

To be clear, most of the water “used” by power plants for cooling needs isn’t actually consumed. Except for whatever evaporates, most of the water ends up back in waterways–albeit a bit hotter.

Still, when it comes to baseload low-carbon power needs, finding a source of cooling water can be a key constraint, cautioned the MIT conference panelists, who spanned industry, academia, and environmental backgrounds.

As it turns out, Palo Verde, where construction began in 1976, was ahead of its time. Essentially all new power plants in America today are unable to secure permits to use freshwater sources for cooling needs, Alexander noted. New regulations coming down the pipe from the US Environmental Protection Agency could also force older, existing plants to switch to recycled water or “dry” cooling techniques that minimize water use.

That’s a key opportunity for entrepreneurs. New technological innovations, thoughtful design and siting, and better recycling and management of power sector water needs are all key to overcoming this potential barrier, the panelists noted.

Out in the desert, freshwater isn’t an option, and it’s probably a long way to the nearest large municipal wastewater treatment plant.

Dry evaporative cooling, or “air cooling,” is the only real option, then, said Colleen Layman, a water treatment engineer with Bechtel Corporation, which helps build power plants all over the world, including the Ivanpah solar plant.

Yet cooling needs at a solar thermal plant are highest during the heat of the day, when power output is greatest. That’s also precisely when air cooling is least efficient, according to John Maulbetsch, a consultant specializing in water management.

This isn’t a challenge for solar thermal alone. Only two nuclear power plants in the world today are air cooled, said Siemens’s Alexander. That’s going to have to change, as new reactors come online in an increasingly water constrained world.

Improving the efficiency of air cooled power plants is just one place where new innovation is needed. Maulbetsch also pointed to improvements in steam turbine designs that can optimize water usage or better facilitate air cooling, while Layman called for better membrane technologies to help treat water discharges from power plants.

Jesse is a researcher, consultant, and writer with ten years of experience in the energy sector and expertise in electric power systems, electricity regulation, energy and climate change policy, and innovation policy.

Nevertheless, new inland pressurized water reactor builds are going to be nearly impossible anywhere with freshwater constraints, which means most of the western United States. Nuclear plants reject more heat for the same electrical power than coal plants, and the minimum nuclear plant build is 2200 MW(e). It’s pretty difficult to imagine finding 2500 MW(e) of older coal-fired turbines in one spot that could be shut down to transfer water rights to the nuclear plants.

I’d like to think that seawater cooled PWRs have a future in the United States. The West Coast especially has a short continental shelf with trenches bringing relatively lifeless water from the bottom. Raising and heating this water can lead to healthy ecosystems like what we have in Monterey Bay. California’s Diablo Canyon site was originally intended for 8 units, but they built just two. I would really like to see 4 new AP1000s built there.

I’ll second the desire to see more LFTR development. High temperature heat rejection to air vastly simplifies the siting and physical security problems.